Following the voices through liminal spaces had a really cool feeling, the shader effects you used also really complement the setting. The second level has a cool sense of monumentality to it and the layer switching mechanic is a nice take on the countdown theme. One thing I would add is to make the visual effects stronger in the last 20 seconds or so of the countdown to build a bit more tension. You could even make the countdown totally diegetic by just making the visual effects gradually stronger until you can't see anymore which is when you switch.